Gov. John Bel Edwards' victory over U.S. Sen. David Vitter in last year's governor's race gives hope to Democrats across Louisiana. If a little-known Democratic state representative could knock off a well-financed two-term incumbent Republican, why shouldn't Democrats also have a legitimate shot at Vitter's Senate seat this November?

Vitter is not running for re-election and Democrats have proven, against the odds, that they can compete in one of the reddest of red states. Even better, this time Republicans are dividing their loyalties among five major candidates, while Democrats have known quantities in Public Service Commissioner Foster Campbell and attorney and business executive Caroline Fayard.

Campbell served 26 years in the state Senate. Fayard lost a 2010 runoff for lieutenant governor to Republican Jay Dardenne, who is now Edwards' commissioner of administration. Campbell seems to have an edge, having earned Edwards' strong endorsement earlier this year.

So, the stars are aligned for a competitive race that a Democrat could win? Well, not so fast.

I'm the first to admit I unwisely discounted Edwards' chances against Vitter. Louisiana voters had not elected a Democrat to statewide office since 2008 and there was little I saw to indicate they would suddenly change their behavior.

What I overlooked was that after eight years of Bobby Jindal's misrule, voters ached for change. No ally of Jindal, Vitter should have been that change - except that Edwards and his allies transformed the race into a referendum on the morally challenged Republican. He went down in a landslide, sunk by voters who were turned off by his 2007 prostitution scandal.

This time, however, the contours of the race are vastly different, meaning that capturing the Senate seat should be far more daunting for a Democrat than was the work of beating Vitter.

While not impossible, it will be difficult to make this race a referendum on personalities. Unlike the 2015 governor's race, the Louisiana Senate election occurs in conjunction with the presidential election, during which ideology and party identification are almost always at the forefront of voters' minds. (It is worth noting that Vitter won reelection in 2010, a mere three years after his prostitution scandal, precisely because ideology, not personality, defined his reelection campaign.)

That means that the Republican who makes the runoff (assuming, of course, that there is a Republican-Democrat election in December) will have a built-in advantage in a state that the Gallup polling organization lists as the nation's third most conservative.

How much does a state's ideological ranking influence its U.S. Senate races? Of the 20 senators representing the 10 most conservative states, only one is a Democrat. Among the 40 senators from the 20 most conservative states, only three are Democrats.

It's not just that Louisiana has become more conservative since President Barack Obama was elected in 2008; it's that it's become dramatically more conservative. Between 1996 and 2008, Republican candidates for the U.S. Senate averaged 45 percent of the state's vote in runoff elections. However, in the two Senate elections since then (2010 and 2014) Republicans averaged 56 percent (Vitter won his 2010 reelection against two Democrats without a runoff).

It's not just Louisiana. No Deep South state has elected a Democratic U.S. senator since former Sen. Mary Landrieu lost to Sen. Bill Cassidy in December 2014. Even when Landrieu was winning her elections, they were by relatively narrow margins (50.2 percent in 1996; 51.7 percent in 2002; and 52.1 percent in 2008). The last time a Democrat decisively won a U.S. Senate seat in Louisiana was 18 years ago, in 1998, when John Breaux (for whom I worked for 17 years) received 64 percent of the vote.

Louisiana's Senate race will most assuredly pivot on ideology and party affiliation if the outcome of a December runoff determines which party controls the Senate. That is not a scenario any Democrat wants.

Could Campbell or Fayard, if one of them makes the runoff, win the election? Sure. Almost anything is possible. And if the Republican candidate is neo-Nazi and former KKK leader David Duke (not likely), Louisiana will elect a Democrat.

But, assuming that a December runoff pits a conventional Republican against a conventional Democrat, it's difficult to envision many of the voters who will cast votes for Donald Trump also pulling the lever for a Democrat.

With five GOP candidates fighting for roughly 50 to 55 percent of the vote (that's 10 or 11 points each, if divided evenly), the best hope for a Democratic victory might be a runoff between Campbell and Fayard.

Don't laugh. This is Louisiana. It's improbable, but stranger things have happened.

Robert Mann, an author and former U.S. Senate and gubernatorial staffer, holds the Manship Chair in Journalism at the Manship School of Mass Communication at Louisiana State University. Read more from him at his blog, Something Like the Truth. Follow him on Twitter @RTMannJr or email him at bob.mann@outlook.com.